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This invention relates to engraving tools and toolholders.
The typical method of engraving or marking surfaces with a toolbit is to hold the toolbit with a rigid toolholder on a numerical control (N.C.) or manual engraving machine and plunge the toolbit down into the surface of the material a set distance. The tool is then moved along the surface of the material and marks are engraved into its surface. The toolbits generally have an angled point on them to produce a very fine mark. As the toolbit is driven deeper into the surface of the material being marked, the mark becomes wider due to the angle on the end of the toolbit. If the material being marked is not perfectly flat or level on the machine table, an uneven mark is produced. The depth of the mark is typically only a few thousandths of an inch, so slight variations in the surface of the material being marked will be seen by uneven engraving. Therefore careful attention must be paid when placing the material to be marked onto the table of the N.C. machine so the surface of the material is exactly level on the machine. If the material being marked has distinct surface irregularities such as a curved surface, the tool must be forced to exactly follow the irregular surface to produce a consistent mark.
Fortier and Roebuck (U.S. Pat. No. 4,991,274) developed a flexible toolholder for a burnishing cutter that uses a spring to provide pressure against the rotated toolbit. The intent of their invention is to thread the tool into the spindle of an engraving machine by means of a thread on the front of the toolholder. The engraving toolbit is held in place with a setscrew in a tool holding element. This setscrew is also the mechanism to prevent rotation of the toolbit within the toolholder. This invention is designed to be used in a specific type of engraving machine with a threaded spindle that could accept such a device. It can not be held in a collet or endmill type toolholder and can not be used on a N.C. milling machine. The toolbit sliding within the main body is the mechanism for retaining the vertical orientation of the toolbit. A precise fit between the toolbit and the main body is needed to prevent the toolbit from wobbling from side to side. If there is an imprecise fit between the toolbit and the main body, the point of the engraving toolbit will wobble from side to side and produce poor engraving. This design requires that a different size main body and tool holding element be produced for each different diameter toolbit that is needed. The spring that is used to provide the force against the toolbit is placed over the outside of the main body and retained by a threaded adjusting member.
Antares, Inc. (Horsham, Pa.) developed a device referred to as the EZ Rider Burnishing Attachment. It is similar to the 30 Fortier and Roebuck design in several ways. The method in which it is attached to the spindle of the engraving machine is via a thread on the front of the toolholder. It is not designed to be held in a collet or endmill type toolholder and can not be used on a N.C. milling machine. The toolbit sliding within the main body is the mechanism for retaining the vertical orientation of the toolbit. A precise fit between the toolbit and the main body is needed to prevent the tool from wobbling from side to side. This requires that a different size main body and tool holding element be produced for each different diameter toolbit that is needed. The toolbit is held in place with a setscrew in a tool holding element. This setscrew is also the mechanism to prevent rotation of the toolbit within the toolholder. The spring is held within the main body via an internal retaining ring.
Sicking (U.S. Pat. No. 3,384,965) developed a tool for holding engraving toolbits that uses an electric solenoid to push down on an engraving point. The engraving point is pushed down towards the surface being marked and is stopped at a preset depth by the invention. The toolholder incorporates a single ball bearing screwed in from the side, which resides in a slot cut into the inner shaft to prevent rotation of the engraving point within the toolholder. The toolholder is used exclusively for scribing the surface to be marked and is not intended to be rotated in a spindle of a N.C. machine while being held with a standard collet or endmill toolholder.
Anfindsen (U.S. Pat. No. 3,753,384) developed an apparatus to adjust the downward pressure of the tool by utilizing an electromagnet. A magnet is used to press down on the toolbit to provide uniform pressure against the toolbit when it is pressed against the material being marked. This device is not intended to be rotated in a spindle of a N.C. machine while being held with a standard collet or endmill toolholder.
Many inventions teach a method for producing pressure against a tool as can be seen by Koenig (U.S. Pat. No. 2,902,760), Johnson et al. (U.S. Pat. No. 2,810,960), Way et al. (U.S. Pat. No. 2,744,329), Braren (U.S. Pat. No. 1,705,957) and Wilkins (U.S. Pat. No. 6,138,365). None of these devices are intended to be held in a spindle of a N.C. machine using a standard collet or endmill toolholder and rotated while still providing constant pressure to an engraving tool. All of these devices require major modifications to be able to use different diameter toolbits.
The present invention relates to a spring-loaded toolholder that applies a relatively constant pressure to an engraving toolbit as it is pushed against the material being marked. The spring-loaded engraving toolholder is held in a collet or endmill toolholder and placed into the spindle of a standard numerical control (N.C.) milling type machine. The toolholder may either be rotated or not by the machine. When the toolbit is pressed against the material being marked and moved along the surface, a constant mark is produced even if the surface of the material is uneven or not parallel to the plane of motion of the machine.
The spring-loaded engraving toolholder of the invention may be easily held with a standard collet or endmill toolholder. When placed into the spindle of a N.C. milling machine or router, it will produce better quality engravings than a rigid (non-spring loaded) tool on uneven surfaces. The spring-loaded engraving toolholder incorporates a collet to hold the toolbit. This allows the toolbit to be easily changed once the spring-loaded engraving toolholder is mounted in a spindle of a N.C. milling machine. A turn of the collet nut is all that is required to release the toolbit from the collet. This also allows different diameter toolbits to be used by simply changing the collet to one having the required diameter.